The primary objective of this study is to characterize the pharmacokinetics and pharmacodynamics (as assessed by whole blood and PBMC glutathione levels) of 10 days of therapy with intravenous Procysteine, 70mg/kg/dose administered q8h (total daily dose: 210 md/kg/day), in patients with cirrhotic liver disease. Secondary objectives are to assess the effect of Procysteine administration on liver function in these subjects, and to determine the effect of Procysteine administration on endotoxin-induced cytokine production in isolated PBMCs.